Signal detectability of marine electromagnetic methods in the exploration of resistive targets
Signal detectability of marine electromagnetic methods in the exploration of resistive targets
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DOI：
10.1111/1365-2478.12151
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发表时间：
2015-01
影响因子：
2.6
通讯作者：
M. Goldman;V. Mogilatov;A. Haroon;E. Levi;B. Tezkan
中科院分区：
文献类型：
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作者：
M. Goldman;V. Mogilatov;A. Haroon;E. Levi;B. Tezkan
我们比较了选定的海洋电磁方法对存在相对较薄的阻性目标(例如，碳氢化合物、天然气水合物、淡水地下水等)的敏感性。研究内容包括常规可控源电磁法、新近推出的垂直电力线瞬变电磁勘探方法和尚处于理论发展阶段的新型海洋圆形电偶极子方法。这种比较是基于一般的物理考虑、分析(主要是渐近)分析以及严格的一维和多维正演模型。结果表明，在浅海地区，垂直电力线瞬变电磁勘探和海洋圆形电偶极子方法是常规可控源电磁法的一种替代方法，后者由于气波现象而效率较低。由于前两种方法本质上都是短偏移距的时域方法，因此无论在浅海还是深海，它们都表现出比可控源电磁法更好的横向分辨率。垂直电力线瞬变电磁勘探和海洋圆形电偶极子方法的最大缺点是难以在海洋环境中准确装配发射机天线。这使得这些方法比可控源电磁法的实用性要差得多。因此，在深海大型阻性目标的探测中，可控源电磁法仍然是海洋电磁技术的主导。然而，对深海小目标和浅海小目标和大目标进行横向探测，可能需要使用不太实用的垂直电力线瞬变电磁勘探和(或)海洋圆形电偶极子方法，作为控制源电磁法的可取替代方法。
We compare selected marine electromagnetic methods for sensitivity to the presence of relatively thin resistive targets (e.g., hydrocarbons, gas hydrates, fresh groundwater, etc.). The study includes the conventional controlled‐source electromagnetic method, the recently introduced transient electromagnetic prospecting with vertical electric lines method, and the novel marine circular electric dipole method, which is still in the stage of theoretical development. The comparison is based on general physical considerations, analytical (mainly asymptotic) analysis, and rigorous one‐dimensional and multidimensional forward modelling. It is shown that transient electromagnetic prospecting with vertical electric lines and marine circular electric dipole methods represent an alternative to the conventional controlled‐source electromagnetic method at shallow sea, where the latter becomes less efficient due to the air‐wave phenomenon. Since both former methods are essentially short‐offset time‐domain techniques, they exhibit a much better lateral resolution than the controlled‐source electromagnetic method in both shallow sea and deep sea. The greatest shortcoming of the transient electromagnetic prospecting with vertical electric lines and marine circular electric dipole methods comes from the difficulties in accurately assembling the transmitter antenna within the marine environment. This makes these methods significantly less practical than the controlled‐source electromagnetic method. Consequently, the controlled‐source electromagnetic method remains the leading marine electromagnetic technique in the exploration of large resistive targets in deep sea. However, exploring laterally small targets in deep sea and both small and large targets in shallow sea might require the use of the less practical transient electromagnetic prospecting with vertical electric lines and/or marine circular electric dipole method as a desirable alternative to the controlled‐source electromagnetic method.